Means for preventing collapse of molded concrete products when core is withdrawn



July 28, 1953 R. o. DAVIS ETAL 2,646,607

MEANS FOR PREVENTING COLLAPSE OF MOLDED CONCRETE PRODUCTS WHEN CORE ISWITHDRAWN Filed June 26, 1948 IN VEN TORS Poberzfi C2 Dov/s 3.- fl/oe/5. Osborne.

ATTO NEYS.

ing the mold and block.

Patented July 28, 1953 MEANS FOR PREVENTING COLLAPSE OF MOLDED CONCRETEPRODUCTS WHEN CORE IS WITHDRAWN Robert 0. Davis and Noel B. Osborne,Adrian, Mich., assignors to Stearns Manufacturing Company, Adrian,Mich., a corporation of Michigan Application June 26, 1948, Serial No.35,348

8 Claims. 1 This invention relates to molding concrete blocks or similarmaterials. In fact, it has broad application to all mold operations.

Concrete blocks are today made largely on automatically operatedconcrete block machines. These operate very rapidly and the result isthat some of the shifting including the withdrawal of the mold and thecores is done very rapidly. This is especially true in a machine such asdescribed in the copending application of Walter G. Schutt,

filed January 14, 1948, on Machine and Method has been recognized, andvents have been provided for the purpose of allowing atmospheric air toenter the space left by the core as it is withdrawn. However, theseopenings very often get clogged with some of the molding material.Furthermore, these openings have to be small in order to prevent thematerial which drops out of I the feed drawer from falling into the ventopen-,

ings. When the core is rapidly'withdrawn the air cannot pass through theopenings rapidly enough to keep the pressure on the inside and outsideof the block equal. In fact, if the mold and cores are stripped from theblock too rapidly they will leave a sufiicient rarified vacuum in theevacuated space to allow the atmospheric pres- [sure on the outside ofthe block to collapse the block. We have accordingly provided a new wayof equalizing the pressure on the outside and" inside of the block asthe mold and cores are stripped from the block. This provides adequateinternal air pressure to prevent the collapse of the box, no matter howfast the stripping action is, and also makes sure that the air passages;

through the cores are never plugged or narrowed by some of thecementitious material getting in the passageways.

Referring to the drawings:

Fig. 1 is a side elevation of a part of a con- 'crete block machineshowing our invention installed.

Fig. 2 is a vertical section of the block showthe core removed from theFig. 3 is a vertical cross section through the mold box and the coresshowing the air system installed.

Fig. 4 is a section on the line 4-4 of Fig. 3.

I designates the customary pallet used in a concrete block machine. 2shows the mold box which has at the top an upwardly extending flangethat is sometimes called a fence 3. This mold box usually consists ofseveral molds to form three or more blocks. Three molds and three cores4 are shown in the drawings. These cores have a slight draft, as isclearly shown in Figs. 2 and 3, to enable the core to be withdrawn fromthe molded block without disturbing the molded surface. Theoutwardly-turned flange 5 of mold box 2 supports a core bar 6, the topof which is recessed at I to form a groove. The top of this groove isclosed by a strip 8 that is welded thereto. This forms an air passagewayacross the top of the core bar. Passageways 9 lead to vent openings I0in each of the cores 4. A passageway. H at the endv of the core barconnects with the T [2 in the air main I3. It will be seen that thereare 2 Ts and one elbow that connect the main with the three core bargrooves .(see Fig. 1). A flexible hose I4 connects the valve I5 with theair main. I6 is a pipe that leads to a source of compressed air.

In molding concrete blocks there is first a shifting of the empty palletunder the mold box, and pushing the pallet bearing the molded block outfrom under the mold box. Next, the mold box is lowered onto the pallet;then the feed or strike-off drawer moves upward from the materialmagazine to a position over the mold box where the contents of thedrawer empty into the mold box to go over the top of the cores and corebars, then there is a vibrating action, then a packer head is loweredonto the mold head with the packer head feet engaging the contents ofthe molds, then a vibration of the packer head follows, then the packerhead is lifted and the mold box and cores are stripped from the block bymeans of an arm I! engaging an angle member H) on the side of the moldbox as shown in Fig. 2. This strips only the core box and the cores fromthe block. It will be obvious that if the cores are lifted out of theblock that little or no air can get to the interior of the block exceptwhat little can sift under the wet blocks standing on the pallet orpassed down on the side of the core between the core and the inside ofthe block. Little or no air can get into the interior of theblock inthis way, consequently, as the core is rapidly lifted in an automaticmaa chine operation the air in the hollow interior of the core and inthe hollow interior of the block, as the core is lifted, becomes muchrarified and there is a substantial difference of pressure on theoutside and the inside of the block, which will ordinarily collapse thewet walls of the said block. This diificulty has been recognized andvent holes have been put in the top of the core to endeavor to remedythis situation, but ob.vi-. ously these vent holes cannot supply air, atatmospheric pressure, fast enough to eliminate the difierential in airpressure on the outside and inside when the core is rapidly lifted outof the block.

We have designed means for overcoming this difficulty by supplyingcompressed air through a conduit on the top of the core bar. Thisconduit guards tops of the vent openings 9 in the core bar and preventsthem from catching and filling up with some of the aggregate falling outof the strike-elf drawer. At the same time, air under pressure affordedby this conduit can equalize the pressure on the inside and outside ofthe blocl; no matter how rapidly core is stripped out of the block.

The amount of compressed air passing into the core must be properly.co-ordinated with the speed of raising the cores. Of course, the fasterthe core is raised the more compressed air will have to be sent into thecore during the raising operation. A cam 20 is timed to trip the leverII that operates a valve if: at substantially at the point of time thelifting of the core begins.

The ventilating openings 9 in the core bar meters the air. The pressurein the shop lines may be near from 80 to 120 pounds per unit area, and,consequently, the greaterthe pressure the more restriction has to beapplied .to letting the air through the air line 6. This is accomplishedby means of the valve and the lever arm 2|. An arrangement may beprovided in this valve for adjusting the lost motion between the lever21 and the valve stem 2d. The more the lost motion the less opening inthe valve and, consequently, this will result in a pressure reductionand this will adapt the air supply to the needs of the block, dependingon the speed of which the cores are lifted. This lost motion may bebetween the lever end and the valve actuator such as a nut 22 on the endof the valve stem.

What we claim is:

1. The method of preventing the collapse of a hollow block in moldinghollow concrete blocgs or similar products when the core is withdrawnand the outer mold stripped simultaneously from the block, whichcomprises the supplying to the space left between the pallet and thewithdrawing core, a charge of compressed air calculated to substantiallyequalize the pressure on the inside and outside of the block as the Goreis withdrawn.

2. The method of preventing the collapse of a i hollow block in moldinghollow concrete blocks or similar products when the core is rapidlywithdrawn and the outer mold stripped simultaneously from the block,which comprises using ahollow core with a vent opening the top andsupplying .a .metered charge of compressed air at a determined pressureto the ho w n or of the core through the vent Ow in said charge of airunder pressure calculated so as to, substantially equalize the pressureon the outside and inside of the block by correlat ng t e air chargewith the speed of withdrawal of thfi core from the block.

3. A mold box containing one or more cores and means for preventing thecollapse of the hollow molded block when the cores and mold are strippedfrom the molded block which comprises the said mold box, the said core'or cores, and a conduit and passageways through the core or cores forsupplying compressed air to the space left by the core or cores in theblock as they and the mold are withdrawn.

4. A mold box containing one or more cores and means for preventing thecollapse of the hollow molded block when the cores and mold box arelifted simultaneously, which comprises the said bold box,'the said coreor cores, and a conduit and passageways through the core or cores forsupplying compressed air to the space left by the core or cores in theblock as they and the mold box are simultaneously withdrawn from themolded block, the air supplied to the space in the block being a chargeco-ordinated to the speed of withdrawal of the core from the block so asto keep the pressure on the inside and outside of the blocksubstantially equalized.

5. A mold box containing one or "more cores and means for preventing thecollapse of the hollow molded block when the cores and mold box arestripped simultaneously from the block, which comprises the said moldbox, the said core or cores, and a conduit and passageways through thecore or cores for supplying compressed air to the space left by the coreor cores in the block as they are withdrawn, the air supplied to thespace n the l ck being a char e O-e u te to the speed of withdrawal ofth core fr m th block so to keep the pressure on the inside and outsideof the block substantially equalized, and a cam and cam-operated valvefor opening the air supply to the block and cutting off the air supplyto meter said air charge.

,6. A mold box containing one or more cores and means for preventing thecollapse of the hollow molded block when the cores and mold box arelifted contemporaneously and rapidly leaving the block stripped, whichcomprises the sa d mold box, the said core or cores united to the moldbox to lift therewith, and a conduit and p agew thr h e c re or coresfor supplying compressed air to the space left by the core or cores inthe block as they are withdraw the air supplied to the space in theblock being a charge co-.-.ordinated to the speed of Withdrawal of thecore from the block so as to keep the pressure on the inside and outsideof the block substantially equalized, a cam and cam-controlled valve foropeni g the supply of air to the space in the block and closin off thesupply of air, the amount of opening of the valve being adjustable bymeans of lost motion between the cam and the valve, and means foractuating the valve adjustable to vary the amount of lost motion and,cons qu ntly, the ope ing o the a ve- 7, A method of preventing thecollapse of molded block walls when rapidly and Simultaneously strippingthe core or cores and the mold from the block in a concrete blockmachine, which comprises simultaneously supplying to the interior of thecores during the stripping operation a metered charge of compressed airto substantially equalize the pressure on the outsi and ins e O t e We sO the 4 dur n the stripping operation.

.8, In a concrete blocl: molding machine, a pa et a m ld n e o e a e b rtemme on the top of the mold, and one or morecores supported by the corebars and each having a hollow open lower end interior and each having aslight draft to permit withdrawal from the block and its seat upon thepallet, passageways through the core bar or bars and into the core orcores, and means for supplying air under compression to the interior ofthe core or cores through said passageways, simultaneously with thestripping of both the mold and the cores vertically upwardly off theblock on the pallet, said compressed air being coordinated toatmospheric pressure by adapting the amount of pressure and metering theair to the interior of the cores so that the pressure on the inside andoutside of the block Wall will be substantially equalized 15 2,297,090

6 during the rapid stripping of both the core 01 cores and the mold fromthe block resting on the pallet.

ROBERT O. DAVIS.

5 NOEL B. OSBORNE.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 1,706,647 Besser Mar. 26, 1929 1,717,996 Moore, Jr.June 18, 1929 2,186,331 Flood et a1. Jan. 9, 1940 2,193,847 Strong Mar.19, 1940 Weaver Sept. 29, 1942

